Preparing lubricating oils using radiation



H. M. HARTZBAND ET AL 2951022 PREPARING LUBRI CATING ons USING RADIA'IION Fled Jah. 24. 1957 Harry M. Honzbund Barry L. Turmy Invenors Robert B. Long PREARG LUBRICATING GILS USING RADIATION Harry M. Hartzband, Westfield, Barry L. Tarmy, Cranford, anrl Robert 3. Long, Wanamassa, N.J., assignors to Esso Research and Engineering Company, a corporaion of Delaware Eiied Jan. 24, 1957, Set. No. 636,066

7 Claims. (Cl. 204-154) The present in ention is concerned with a continnous process for producing high-quality lubricating oils frorn paraflinic feed stocks through the use of high energy ionizing irradiation.

In brief compass this invention proposes a process compnsing irradiating a predomnantly parafiinic feed boiling in the range of about 100 to 700 F. with high energy ionizing radiation at a temperature in the range ahove the pour point of the feed (ca. 50 F.) to 700 F. until at least kilowatt-hours/pound (kW. h./lb.) of radiation have been absorbed to obtain a conversion of at least 1 Wt. percent of the feed per pass. The material so irradiated is then separated to recover an intermediate boiling range (ca. 750/950 F.) lubricating fraction having a viscosity in the range of 35 to 70 SSU at 2l0 F. althougn it can be hi her, and a viscosity index (V.l.) above 120. The material boiling below this interrnediate boiling range fraction is recycled to the radiation zone.

It has now been found that the product obtained by irradiating a parafinic feed material shows a rather unique variation of viscosity index with viscosity, as compared with conventional lubn'cating distillates. As expeoted, the irradiated material increases in viscosity as the bciling point goes up. The viscosity index for irradinted materials reaches, however, a maximum at sorue intermediate viscosity. This is not true for conventional lubricating distillates as they show a relatively flat but decreasing viscosity index with increasng viscosity.

The present invention incorporates this surprising finding into a continuous process typified by recovery of a high V.I product. The process of this invention also embodies several other important features.

The drawings attached to and forrning a part of this specification, and the following explanation and examples, will serve to make this invention clear. In the dravvings, Figure I presents schematically the process of this invention, and Figure H presents a graph illustrating the unexpected relationship between viscosity and viscosity index of the irradiated product.

The feed material for the present nvention boils in the range of 100 to 700 F. -It usually has a viscosity below 35 SSU at 210 F. and is not generally considered a material suitable for lubricating purposes. The feed material used is predominanhy paraflnic. By this is meant it contains at least 75 vvt. percent of parafiinic hydrocarbons. It is preferably 10W in aromatics, both single and condensed ring, i.e., the feed material contains less than 5 wt. percent aromatics. It may contain some oleiins and naphtnenes within the boiling range, but preferably these do not exceed about 25 wt. percent. The feed stock may also contain up to 20 Wt. percent of low molecular weight, or light, C C unsaturates such as e=thylene, and/or sorne light, C C saturates such as Patented Aug. 30, 1960 as Fischer-Tropsch synthesis products, shale oils, and refinery stream such as catalytic cycle stocks. In most instances it is desirable to treat the feed material to meet the above limtations. This may be done by such means as extraction with sulfur dioxide or furfural, by precipitation such as with propane, by adsorption as with silica gel, by dewaxing, by crystallization, besides by distiliation or fractonation, and combnations thereof, all of which methods are known in the art.

With reference to the drawing, the above described feed material is introduced by line 1 into an irradiation zone 2, to be treated according to this invention with hi h energy ionizing radiation. By high energy ionizing radiation is meant radation from terrestrial sources consisting of photons having a wave length less than 50 A. such as gamma and X-rays, rapidly moving charged or uncharged particles of an atomc or subatomic nature having an energy above 30 ev., such as alpha particles and beta rays, and neutrons, the radation heing of sufficient intensity such that the dose rate is at least l. 10 kW. h./lb./hr This excludes radiation such as cosrnic and ultraviolet. lt is rnuch preferred to use radiaton comprising neutrons such as that obtained from a nuclear reactor, so that at least 30% of the energy receved is obtained from the neutrons.

The feed material is rradiated to an extent suficient to obtain the product characteristics described helow. The material receives a close of at least 5 10" kw. h./ 113., based on fresh feed, and over-irradiation is to be avoided. The maximum amount of radiation usecl should be ander 1 kW. h./lb. based on fresh feed. The ra'te of rradiation is somewhat important. If it is too low, the excited molecules are too dluted to effectively react; and if over-extensive, cracking predominates to polymerzation. While the invention is operable in the range of 1 to 50 10 kw. h./lb./hr. best results are obtained in the range of 4 to 8.

The irradiaton can be obtained fIOI1 any convenient source such as charged particle accelerators, e.g. Van de Graaff generators and Betatrons; from nuclear reactors, e.g., atomic piles; waste materials frorn nuclear reactors e.g. spent fuel elements; and materials made radioactive by insertion into a nuclear reactor, e.g., cobalt 60. The use of an atomic pile Wherein mixed gamma and neutron irradiation is obtained is much preferred. This means that the feed material should be substantially free (contain less than 0.5 Wt. percent) of non-hydrocarbon materials that may become radioactive by neutron irradiation, such as sulfur and chlorine.

The feed material is exposed to the irradiation in any convenient manner. For example, if an atoinic pile is used, the feed material can smply be flowed through suitable conduits or pipes, in, around, and through the pile. The position of the feed material containng conduits within the pile partially deterrnnes the intensity of rradiation.

The pressure during irradiation is not too important, it generally being suflicient to maintain condense phase conditions. Pressures used can range from 0 to 4000 p.s.i.g., or above. The temperature is important. Whle this inventon is operable at temperatures up to about 700 F., best results are obtained at temperatures in the range of 300 to 600 F. Excessively high temperatures result in a loss of product to cracking reactions, and low temperatures may undesirably decrease the reaction rate besides undesirably affecting the product characteristics.

When using pile irradiation, which comprises neutrons, it may be desirable to add to the feed isotopes that, upon capture of a neutron, admit highly energetic secondary irradiation. Thus, boren 10 and/or lithium 6 can be added to the feed material to create highly ionzing alpha particls. Cadmium 113 can be used to create highly energetic gamma rays from the neutrons. These materials can exist in amounts in the range of 0.001 to 1 wt. percent as soluble compounds, as discrete subdivided solids,

or can be distended on the surfce of radiation inert solids.

As previously indicated, the irradiated material is withdrawn by line 3 before it is over-irradiated, and is separated in zone 4 to recover a product that has a surprisingly high V.I. The products obtained by the irradiation can include dry gas, C s gasoline 430), heating oil (430/600), light lube (600/900), bright stock (900/ 1200), and higher molecular weight polymer.

The irradiated product can be separated in zone 4 in any convenient manner. Distillaticn is usually sufficient. A product of suitable viscosity and intermediate boiling range is separated and removed by line 5. This intermediate fraction, boiling in the range of 750950 5., and more preferably 800875 R, is obtained in yields of about 1 to 20 wt. percent per pass, based on fresh feed, and has a viscosity in the rangeof 35 to 70, or above, SSU at 210 F., and a viscosity index of at least 120. With recycle operation ultimate yields of over 80 wt. percent are obtained. t has been observed that the concentration of the desired intermediate boiling range fraction bulds up to a maximum during recycle of about 12 wt. percent. Beyond this the intermediate fraction appears to be converted to heavier material as fast as it is being formed. For this reason, it is desirable that the recovery of the intermediate fraction be such that its concentration in the feed be substantially below 12 wt. percent.

The material of lower ooiling range than the product is removed by line 6. The higher boiling material is removed by line 7. The high V.I. product removed by line 5 can, of course, be further treated by other means in separation zone 4 if desired. Thus, a molecular type separation as dewaxing, extracticn of aromatics as by silica gel or solvent treating can be used to separate low V.I. components from the high V.I. product. These low V.I. components of about the Same bciling range as the high V.. product. are remmred by line 8.

While some of the light material removed by line 6 can be withdrawn as product, preferably a major portion and usually about all of this light material is recycled by line 9 to the irradiation zone te be further converted into the desired high V.I. product. If desired, some of the extrernely light components in the material in line 6, i.e. the C gases, can be removed and discarded.

As will be appreciated by those skilled in the art, better cont=rol of the irradiated product can be obtained by re cycling a substantial proportion of the irradiated material before such separat-ion. This can be done by line 110. By using recycle, the rate of polymerization and the dosage receved by the material is more readily controlled and overdrradiation is easily avoided.

Data also indicates that the product in line 5 can be further increased in viscosity by 5 or more units, With little loss in V.., by further separately irradiating it in the absence of diluting er contaminating lower or higher boiling components. Thus, in one embodimnt of the invention, a portion or all of the product in line 5 is recycled to be separately irradiatd by line 11'. The conditions here are substantially those used in irradiating the feed material.

The polymer bottoms in line 7 can be disposed of as desired. They are useful as lubricants of the cylinder or bright stock type, and usually have a viscosity at 210 of 150 SSU or better. either thermally, catalytically, or by irradiation as shown by line 12, to recover some of the over-polymerized feed material, and. the depo-lymerized cracked material can be recycled to zone 2 if desired to be again converted, by itself or witl1 fresh feed, into the proper viscosity range material. 7

If a separatiorr for a low V.I. product be made, then They can be subject to cracking the material inline 8 can be recycled and further converted either alone with the feed, or can be combined with the contents of line 7 for thermal cracking. In this way the yield of the process is further increased.

Example I 600 cc. of substantially pure cetane (nhexadecane) were irradated in the Brookhaven National Laboratories atomc pile in a vented aluminurn container. The container was maintained at a temperature of 260 F.and at a pressure of abo ut 1 atrn. The flux in the container was about 3 X10 neutrons per square centimeter per second (n/cm. /sec.) and 1.6 megaroentgens/hour of gamma radiation (1 megaroentgen is equivalent to about 1x 10 kw.h./ 1b. The irradiation was continued for about s days until 300 megaroentgens had been absorbed.

Upon exarnination of the irradiatd material, it was found that the viscosity index reached a maximum at about 40.SSU -at 210 F. This irradiated material was separated to obtain a fraction boiling in the range of about 700 to 900 F. This fraction had a viscosity of 38.5 SSU at 210 F. a viscosity index of 145, and a +40 F. pour point. It could be dewaxed to a 0 F. pont by rernoving 3.5 wt. percent wax and did not break down under shear.

Example II 42,362 grams of cetane were passed from a storage drum at a rate of 1500 cc./hr. through an aluminurn reactor having an inside diameter of 2 inches and a length of 12 feet. The reactor was located in an unused fuel channel near the center of the Brookhaven pile. The ap proximate flux was 0.2 10 n./cmP/sec. of fast neutrons, 1 10 n./cm?/ sec. of thermal neutrons, and 1 10 R./hr. of gamma rays. The pressure was about atmospheric and the temperature was 200 to 400 F. varying with the length of the reactor. The material from the reactor was passed through a condenser at 65 F. The liquid product was returned to the storage drum for recycle and the gas was metered and vented. The yields, as weight percent on feed, after 3140 hours of operation were:

Gas 2.3 0/430 F. 1.5 430/540 F. 3.1 540/600" F. (feed) 71. 560 F.+ 21.2

Figure II is aplot of the surprising results obtained from the continuous conversion of cetane. The graph gives the viscosity and viscosity index, as the ordinates.

of incremental fractions distilled from the irradiated rriaterial, the incremental fractions being expressed on the abscissa as being obtained at a certain weiglrt percent distilled ofif. The point was at 600 F. (atrn. eq.) the point was at 835 F., and the point was at 925 F.

This exarnple illustrates the surprising relationship between viscosity and viscosity index of the irradiated ma terial, and shows the unexpected results to be obtained through recycle operation with continuous recovery of a select intermediate boiling range fraction.

Having described this invention, what is sought to be protected by Letters Patent is succinctly set fcrtn in the following claims.

What is claimed is:

1. A process comprising irradiating a predorninantly paraffinic feed stock boiling in the range of to 700 F. and having a viscosity below 35 SSU at 210 F. with high energy ionizing radiation having an energy level above 30 electron volts, at a rate in the range of 1 to 50 10- kw. h./lb./hr. and at a temperature up to 700 F. until at least 5 10* kw. h./lb. of radiation are absorbed, separating the material so irradiated and recoverng an intermediate boiling range distillate fraction havng a viscosity above 35 SSU at 210 F. and a V.I.

above 120, and recycling a portion of the irradated material boiling below said intermediate fraction.

2. The process of claim 1 wherein said feed stock contains up to 20 wt. percent of C C hydrocarbons.

3. The process of claim 1 wheren said intermediate boling range fracton is further irradiated to increase the viscosity thereof by at least 5 units.

4. The process of claim 1 wherein a portion of the irradated material is directly recycled before separation, and the recovery of said intermediate boilng range fraction is such that the concentration thereof in the feed is below 12 wt. percent.

5. The process of claim 1 wherein said irradiation is obtained from a nuclear reactor and comprises neutrons and gamma rays.

6. A process comprsing irradiating a feed stock boiling in the range of 100 to 700 F. having a viscosity below 35 SSU at 210" F. and comprising at least 75 wt. percent paraflns and under 5 wt. percent aromatics, with high energy ionizing radiaton having an energy 1evel above 30 electron volts at a rate in the range of 4 to 8X10 kw. h./lb./hr. and at a temperature in the range of 300 to 600 F. until 5 to 600 10" kw. h./lb. of radaton a1c absorbed, recovering the irradiated material, directly recycling to the feed a portion thereof to control in part the degree of oonversion, separating the rema.inder to obtain an intermediate fraction boiling in the range of 800 to 875 F. and having a viscosity in the range of to SSU at 210 F. and a viscosity index of at least 120, and recycling to the feed "a major proporton of material from the separaton step bolling below said intermediate fracton.

7. The process of claim 6 wherein said high energy radiation is obtained from a nuclear reaction and wherein at least 30% of the energy absorbed by said feed stock is derived from neutrons.

References Cited in the file of ths patent UNITED STATES PATENTS OTHER REFERENCES Mincher Knolls Atomic Power Laboratory Report 731, April 2, 1952, pp. 1-8. 

1. A PROCESS COMPRISING IRRADIATING A PREDOMINANTLY PARAFFINIC FEED STOCK BOILING IN THE RANGE OF 100 TO 700*F. AND HAVING A VISCOSITY BELOW 35 SSU AT 210*F. WITH HIGH ENERGY IONIZING RADIATION HAVING AN ENERGY LEVEL ABOVE 30 ELECTRON VOLTS, AT A RATE IN THE RANGE OF 1 TO 50X10-3 KW. H./LB./HR. AND AT A TEMPERATURE UP TO 700*F., UNTIL AT LEAST 5X10-3KW.H./LB. OF RADIATED AND REABSORBED, SEPARATING THE MATERIAL SO IRRADIATED AND RECOVERING AN INTERMEDIATE BOILING RANGE DISTILLATE FRACTION HAVING A VISCOSITY ABOVE 35 SSU AT 210*F. AND A V.I ABOVE 120, AND RECYCLING A PORTION OF THE IRRADIATED MATERIAL BOILING BELOW SAID INTERMEDIATE FRACTION. 